The feed rate of conveyor belts, i.e., the amount (e.g., expressed by the mass or the volume) of bulk material conveyed per time unit, is controlled by adjusting the conveying speed. Such a control system has the disadvantage that, in particular in case of long conveyor belts, a large quantity, i.e., mass, of conveyed material has to be accelerated or slowed down for each adjustment of the feed rate. This has a negative effect on the energy efficiency and characteristics of wear of the components of the conveyor belt. In addition, the inclination of the conveyor belt has to be adapted to the changed conveying speed for conveyor belts in which the discharged material flow should hit a certain point so that the same point can be hit even after a change of the conveying speed.
Dosage sliders that regulate the size of a throughput opening of a conveyor tunnel through which a conveyor passes are known from the applicant's DE 93 08 170 U1. For this purpose, they are slid vertically from the top towards the conveyor in order to limit the quantity of material transported on such conveyor. Such a configuration can in particular be disadvantageous in case of conveyor belts with a trough-like shape as the geometry of said dosage slider has to be adapted to the trough shape of the conveyor belt in this case to ensure a feasible limitation of the material flow. The trough shape of the conveyor belt, however, can depend on the mass and the structure of the conveyed bulk material; an adapted form of the dosage slider, in turn, can only be suitable for one specific trough form. In particular in case of flat conveyor belts, a lateral spreading of the bulk material is facilitated by a dosage slider that is moved into the material flow from the top, whereby material may fall laterally off the conveyor belt. In addition, bulk material might roll to the side and also fall laterally off the conveyor belt in case of trough-shaped conveyor belts in an area ahead of a pulley in which the trough-shaped conveyor belt transitions into a flat form in order to ensure smooth passage of the conveyor belt around the pulley, i.e., during so-called detroughing of the conveyor belt.